Piston-type accumulators are, in the broadest sense of the term, hydraulic accumulators, which among other things serve the purpose of receiving specific volumes of a pressurized liquid (hydraulic medium) of a hydraulic system and returning these volumes to the system when required. Since the hydraulic medium is pressurized, hydraulic accumulators are treated as pressure reservoirs and must be designed for the maximum excess operating pressure, the acceptance standards of various installing countries being taken into consideration. Hydropneumatic (gas-charged) accumulators with a separating element are currently used in most hydraulic systems. A piston separates a fluid space as working chamber from a gas space as additional working chamber, serving as separating element inside the accumulator housing of the piston-type accumulator. Nitrogen is generally used as the operating gas. The gas-tight piston to a great extent permits disconnection of the gas space from the fluid space.
The fluid component is connected to the hydraulic circuit so that, as the pressure rises, the piston-type accumulator admits or receives fluid and the gas is compressed in the process. As the pressure drops, the compressed gas expands and displaces the pressurized fluid back into the hydraulic circuit. One advantage of piston-type accumulators is they can “work” when in any position, but preference is given to vertical positioning with the gas side on top, so that settling of fouling particles from the fluid on the piston seals is prevented.
Consequently, the essential components of a piston-type accumulator are an outer cylindrical tube forming the accumulator housing, the piston forming the separating element with its sealing system, and the sealing covers on the housing ends. The cover elements also contain a fluid connection and a gas connection. Two functions are regularly assigned to the accumulator housing, specifically storage of internal pressure and ensuring control of the piston inside the accumulator housing. The cover components on the front surface sealing the interior of the accumulator housing off from the exterior are provided on the outer circumference with external threading which may be screwed into a corresponding inner threading along the free longitudinal edge over an assigned path. Production of the respective threaded connection is time-consuming; and correspondingly increases the production costs of the piston-type accumulator. In addition, safety measures must be taken to secure the cover component in its position.